Method and apparatus for optical fiber curve follower including method and apparatus for making position scale therefor



Sept. 24, 1968 c. w. HARGENS 3,403,263

METHOD AND APPARATUS FOR OPTICAL FIBER CURVE FOLLOWER INCLUDING METHODAND APPARATUS FOR MAKING POSITION SCALE THEREFOR FiledOct. '16, 1964 2Sheets-Sheet 1 no.2; 2139 2 FIG.

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- Sept. 24, 1968 c. w. HARGENS m 3,403,263

' 1 METHOD AND APPARATUS FOR OPTICAL FIBER CURVE FOLLOWER INCLUDINGMETHOD AND APPARATUS FOR MAKING POSITION SCALE THEREFOR Filed on; 16,1964 '2 Sheets-Sheet 2 v I 78X 7 OTORS 64X 7 .1 PHOTOCELLS CLUTCH 6XXcpurcn NTIOMETER 3 /40 FIG. 13.

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United States Patent.

3,403,263 METHOD AND APPARATUS FOR OPTICAL FIBER CURVE FOLLOWERINCLUDING METHOD AND APPARATUS FOR MAKING POSITION SCALE THEREFORCharles W. Hargens III, Philadelphia, Pa., assignor to The FranklinInstitute, Philadelphia, Pa., a corporation of PennsylvaniaContinuation-impart of application Ser. No. 272,013, Apr. 10, 1963. Thisapplication Oct. 16, 1964, Ser. No. 404,218

16 Claims. (Cl. 250-202) ABSTRACT OF THE DISCLOSURE A curve followerincluding a movable scanning head suported on a bridge structure whichin turn is movable relative to a curve support base. Drive means aresupplied to move the scanning head and other drive means are supplied tomove the bridge. The scanning head contains a plurality of opticalfibers in a closely grouped array positioned to pick up light reflectedfrom the curve illustration when associated with individual photocells.The fibers and photocells are preferably divided into at least twogroups, one group of which is designed to actuate the scanning headdrive member and the other group of which is designed to actuate thebridge drive member. A switching circuit is provided whereby uponpredetermined conditions one group of photocells or the other iseffective and the drive means for the other group is connected to apower source to provide an independent drive movement. Preferably scalemeans is provided using additional sensing heads movable with thescanning head and the bridge means respectively and cooperating withscales on the structure relative to which this movement occurs, whichscales have patterns which are unique for each position of therespective sensing heads. The coded scales for the sensing heads may bemade using light sensitive strips and transmitting light through thefibers intended to sense light or dark of the scale to provide a uniquepattern of light and dark across each row representing a given positionor station of the associated movable means.

This invention relates to optical transducer means employing the art offiber optics, and, more specifically, to transducer devices employingthe ends of optical fibers in a close spaced relationship for thepurpose of either sensing light from a surface or optically creating apattern on a surface.

This is a continuation-in-part of my US. patent application, Ser. No.272,013, filed Apr. 10, 1963 and now abandoned.

The present invention advantageously makes use of a filamentaryphotocell device described in my US. Patent No. 3,310,680 entitledOptical Filamentary Photocell Device Having Spaced Electrical ConductorsArranged in a Matrix and dated Mar. 21, 1967. In the specification anddrawings of that patent, there is described a filamentary photocelllocated around the periphery of an optical fiber, which has beenroughened in that region by etching to permit local emergence of light.The roughened zone is coated with a photosensitive electricallyconductive material and is provided with electrodes at the ends of thezone which are connected to elertrical conductors which are used toconnect the photocells to any desired circuit. The photosensitive areasare covered with an opaque lightexcluding jacket or sheath to preventconfusion of fiber transmitted signals with those which might otherwisebe generated by external ambient lighting.

3,403,263 Patented Sept. 24, 1968 ice It is well known in the art thatfiber optics is based upon the use of very small fibers of glass or alike mate rial which conduit light along their length by the process oftotal internal reflection. Ordinarily the fibers may be turned ortwisted out of alignment with the position of their pickup end withoutdistortion, deterioration or loss of the light conducted. Fibers may bethinner than human hairs, having diameters of .001 inch or less in somecases, although they may be larger as the occasion requires. Theirusefulness in connection with the present invention, however, depends toa large extent upon their smallness in size, at least relative to thelines or patterns observed or monitored by the fibers.

It is known to group fibers together for the purpose of transmitting apicture or an image of an object from one location to another, forexample. It is also known to use individual fibers as transmission linesfor coded information. Until the advent of my co-pending invention,however, it was not known to use fibers in groups or arrays to producecoordinated coded signals. The use of fibers in this manner is feasiblebecause of the inherently small sizes of the fibers involved. Inaccordance with the present invention, fiber arrays are used with theirsensing ends fixed in a predetermined array which is not used fortransmitting a picture, but rather either for sensing a contrasting lineor contrasting pattern on a surface or for following a curve undercertain circumstances.

One example of a use of the present invention is in a line sensingoperation. The fiber ends may be arranged in a predetermined patternwherein, for example, a dark line on a light background will be sensedby the lack of reflection of light from the line as compared to the restof the surface which does readily reflect light. In preferredembodiments, the fibers may be arranged such that they produce signalswhich initiate or continue movement, driving the scanning headcontaining fiber ends, for example, by actuating movement of thescanning head in at least one direction. Such an action coupled with.transverse independent drive motion enables curve following which isone of the primary functions of the present invention.

A typical curve follower in accordance with the present invention, aswith most two dimensional curve followers, involves a pair of axesordinarily, but not necessarily, at right angles to each other andordinarily a curve which may typically be on paper supported on a fiatsupport base. Bridge means moves across the support base in apredetermined manner in accordance with and in response to bridge drivemeans. A scanning head moves in a predetermined path along the bridgetransverse to the direction of movement of the bridge and is alsoprovided with a drive means. The scanning head is provided with aplurality of optical fibers having their ends fixed in a closely groupedarray to pick up light reflected from the curve bearing surface. Inorder for the device to be operable, a photocell is provided for andassociated with each of the optical fibers. Each of the photocells iscoupled to appropriate circuitry which is associated with one of thedrive means. The circuitry effectively couples the Photocells and thusrelated fibers to suitable means for 0perating the respective drivemeans to cause the fiber array or sensing head to center on the curve,In the preferred embodiment of operating the present invention, onedrive motor is coupled by the circuit means to selected photocells tocause centering on the curve, while the other drive means is arranged tooperate independently. Preferably, as will be described hereafter, therespective drive means may be switched from one function to the other.

Such a curve follower has limited usefulness unless means is alsoprovided to record the coordinate positions of the scanning head atleast periodically. In accordance with the present invention, sensingmeans, like that used to sense and follow the curve, may be used totrack coded scales in the direction of movement of the bridge and in thedirection of movement of the scanning head. The scales are preferablylocated along the support base and bridge, respectively, and are trackedby sensing means located on the bridge and scanning head carriages,respectively.

In accordance 'with the present invention, the same type of positionsensing means useful to sense coordinates in a curve-following deviceare useful in other applications to indicate coordinates, or for othersimilar purposes. Further, the system used to follow the coordinates canbe used in reverse with some modification to make the coordinate scales,or scales for some other purpose, useful with such fiber array sensingheads. There are numerous alternate means of accomplishing these resultsand several of these will be discussed hereafter.

For a better understanding of the present invention, reference is madeto the following drawings, wherein:

FIG. 1 is a plan view of a coordinatograph or mechanical draftingapparatus in accordance with the present invention providing curvefollowing and coordinate recording functions;

FIG. 2 is an enlarged side elevational view of the carriage supportingthe curve following scanning head and related apparatus taken along line2-2 of FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 1 showing thecarriage supporting bridge structure in elevation;

FIG. 4 is a schematic diagram of the photosensing means and a preferredoverall electrical system of the curve following apparatus shown inFIGS. 1-3;

FIG. 5 is a schematic diagram showing the light sensing fiber ends inthe scanning head of FIG. 4 in relation to a section of a curve;

FIG. 6 is a schematic view of another possible arrangement of theoptical fiber ends in the scanning head;

FIG. 7 is a view similar to FIG. 5 showing the preferred arrangement ofthe fiber ends in the scanning head;

FIG. 8 is a view similar to FIGS. 6 and 7 showing a still differentarrangement of the fiber ends;

FIG. 9 is a view similar to FIGS. 6-8 showing still another arrangementof the fiber ends;

FIG. 10 is a view similar to those of FIGS. 69 showing an arrangement oflight sensing fiber ends in a sensing head for following a codedcoordinate scale used to identify position along one of the axes of theapparatus of FIGS. 1-3 and is a view taken along line 1010 of FIG. 3;

FIG. 11 is a greatly enlarged diagrammatic plan view of a portion of abinary decimal coded coordinate chart showing the equivalent decimalnumbers;

FIG. 12 is a schematic representation showing an optical fiber recordingarrangement which may be used alternatively to create a chart or readcoordinate positions from a chart of the type shown in FIG. 11, thelower part of the diagram from the broken portion of the fibers beingalso representative of a sectional view of the sensing head taken alongline 12-12 of FIG. 1;

FIG. 13 is a schematic representation of alternative apparatus to theone shown in FIG. 12 which may be used to create or read codes of thegeneral type shown in FIG. 11; and

FIG. 14 is a schematic side elevational view of a recording devicesomewhat similar to the one shown in FIG. 12 using a band arrangementinstead of a drum arrangement for movement of the chart.

Referring first to FIGS. 1 to 3, a coodinatograph of the general typefamiliar to drafting rooms is illustrated. However, this device has beenmodified in accordance with the present invention in order to enable itto follow curves placed on the base 10, which preferably is a draftingtable or enlarged drafting board. This present invention in thepreferred arrangement provides the scanning head 11 with two degrees oflinear motion in order to follow a selected curve C on curveillustration 12 fixed to table 10. The curve illustration may, ofcourse, be made directly on the base or on a separate surface, usuallypaper, supported on the base. The movement of the scanning head is donewhile keeping the head in the attitude relative to and at a minimumheight above the surface of the base for adequate pickup of reflectedlight from the curve illustration and without any component ofrotational movement. The two degrees of movement over the plane surfaceof the base are advantageously right angle coordinate movements whichmay be familiarly expressed in terms of positions with respect to ahorizontal X-axis and a vertical Y-axis. Movement of the curve scanninghead along the Y-axis is permitted, as shown in PEG. 2, by mounting thescanning head 11 on a carriage generally designated 14 which is movableparallel to the Y- axis along a bridge structure generally designated15. Bridge structure 15 is oriented parallel to the Y-axis and is mademovable relative to the base 10 along the X-axis. Thus, movement ofcarriage 14 along the bridge adjusts the position of the scanning head11 in the Y-axis direction, whereas movement of the bridge as a wholerelative to the base 10 results in movement of the scanning 11 to senseany coordinate poistion over the total area behead in the X-axisdirection. The combination of movements along the X- and Y-axis enablesthe scanning head ing monitored.

The scanning head 11 is made up of a grouping or array of optical fiberends, which will be described in greater detail hereafter. The scanninghead which is preferably of a transparent material such as an epoxyresin to allow illumination of the curve illustration beneath the headfrom the side thereof is supported by a tubular casing 17 terminating onhousing 18, which elements may contain the fibers, filamentaryphotocells and suitable circuitry, which will be described hereafter,for sensing curve position and initiating movement of the bridge orcarriage. The scanning head structure as a whole is supported on abracket 20 fixed to slide 22 which is the guide member of the carriageand advantageously has a keyed portion snugly accommodated in a suitableguide slot 23 in and extending along the bridge structure 15. A suitablebracket 24 on the housing 17 supports a lamp 26 positioned to directlight to the area immediately beneath the scanning head, which lightilluminates the area in such a way that from a reflecting surface it iscapable of reflection back into the ends of the fibers of the scanninghead at such an angle as to be acceptable for transmission through thefiber by its total reflection process.

The bridge structure 15, as best seen in FIG. 3, consists of the mainbridge span 28 which provides the slot 23 in which the carriage supportmember 22 rides. The bridge extends generally parallel to the base 10almost entirely across across the base parallel to the Y axis andterminates at its ends in flange members 29 and 30. Between flanges 29and 30 and parallel to the span 28, there extends a deck 31 whichpreferably supports a calibrated coded scale 32 from which the locationof the carriage 14 relative to the bridge 15 may be determined.

A code sensing head 35, which is preferably of a transparent materialsimilar to scanning head 11, is suitably supported on slide 22 ofcarriage 14 and cooperates with the coded scale 32 to determine theposition of the carriage relative to the bridge and hence determiningthe Y coordinate of the scanning head 11. Slide 22 also supports bysuitable bracket means a light 36 which illuminates the portion of thecoded scale 32 beneath the code sensing head 35. The code sensing head35 is provided with an array of optical fibers whose ends are preferablyarranged as is shown in FIG. 10, an inverted plan view of the sensinghead. The nature and operation of the code sensing head will bedescribed in greater degree hereafter.

Movement of carriage 14 along the bridge is provided by suitable drivemeans, preferably a motor 38, which may be supported on bracket 29, withits shaft vertically orientated, carrying a sheave 39 and positioned atone end of the bridge beyond the range of carriage 14 as determined bythe extent of slot 23. A similar sheave 40 is located at the oppositeend-of the bridge, likewise out of range of the carriage movement.Actual movement of the carriage is accomplished by band 42, which hasits opposite ends connected to carriage 14 in any suitable manner, suchas by thumb screws 43 which engage and hold the ends of band 42 withineyelets on the carriage and specifically on the slide 22 thereof. Theband 42, which is preferably of steel tape or wire, extends around thesheaves 39 and 40 and when drawn sulficiently taut will cause the slide22 and carriage 14 as a whole to move in one direction or the otheralong the bridge in response to the rotation of motor 38 in onedirection or the other.

The bridge structure 15 carries a code sensing head 45 of a transparentmaterial similar to the Y coordinate code sensing head 35. Code sensinghead 45, however, cooperates with a coded scale 46 located on base andarranged to extend and identify coordinate positions in the X-axisdirection. Coded scale 46 is, of course, coded to give the X coordinateposition of the bridge just as the coded scale 32 gives the Y coordinateposition of the carriage 14. Code sensing head 45 is preferably providedwith an illuminating light similar to lights 26 and 36 to illuminate thearea immediately beneath the code sensing head.

The bridge is supported at flange 29 by a wheel 48 which is supported bysaid flange and whose axis of rotation extends in the direction ofbridge extension. The wheel is adapted to run on a track 49 located onthe base 10 parallel to the X-axis. The other end of the bridge issupported from flange and deck 31 by a tubular guide member 51 whichsnugly encloses and rides on a rail 52 which extends parallel to theX-axis. Rail 52 is supported at its opposite ends from the base 10 bysuitable brackets 53 and 54. Bracket '53 preferably also supports thebridge drive means, motor 56, whose shaft carries sheave 57. Bracket 54carries idler sheave 58 on a shaft parallel to the shaft of motor 56. Asuitable band 59, similar to band 42, has its ends afiixed to tubularmember 51, such as by thumb screws 55, and extends around sheaves 57 and58 in an open loop. If the band 59 is maintained sulficiently taut, thebridge will be moved in a positive or negative X-axis direction inaccordance with the direction of rotation of the motor 56, as the resultof corresponding direction of movement of the tubular member 51.

Considering now the schematic drawing of FIG. 4, as well as FIGS. l-3, apreferred embodiment of the overall system of the curve follower isillustrated. As can be seen in FIG. 4, the curve following scanning head11 is shown schematically much enlarged as it follows a short portion ofcurve C. In this embodiment of the scanning head there is an orthogonalgrouping of the optical fiber ends so that one group is parallel to theX-axis and the other group is parallel to the Y-axis. Both groups offibers at their ends, of course, extend generally normal to the surfacebeing monitored. The horizontal or X-axis group of fibers is designatedfor the sake of convenience X fibers and are numbered outward X1, X2,X3, and X4, respectively, from the center to the right and X1, X2, X3,and X4, respectively, from the center to the left. In similar manner thefibers parallel to the Y-axis are identified Y1, Y2, Y3 and Y4 from thecenter upward in the positive Y-axis direction and Y1, Y2, Y3 and Y4from the center downward in the negative Y-axis direction. Remote fromthe sensing head 11, the fibers, which in practice extend upwardly intothe casing 17, may terminate in the housing 18 (see FIG. 2) infilamentary photocells of the type disclosed in my United States PatentNo. 3,310,681, referred to above.

In FIG. 4 filamentary photocells associated with the X fibers are shown.These photocells are grouped and generally designated 62X and 62X,respectively, in adjacent arms of the X coordinate bridge 64X, thephotocells being associated with the X1, X2, X3, and X4 fibers and theX1, X2, X3 and X4 fibers, respectively. The groups of filamentaryphotocells 62X and 62X in adjacent arms of the bridge circuit 64X arearranged with group 62X being connected in parallel in one arm, andgroup 62X are connected in parallel in an adjacent arm. Preferably,connected in series with each of the photocells is a resistance. Theseresistors have been grouped with resistors 63X being associated withcells 62X and resistors 63X associated with cells 62X. The individualresistors are connected in series with individual photocells within theparallel connection of cells, thereby effectively increasing the totalapparent resistance of each photocell. The resistors may all be equal insize or in each group may be graduated in resistance, the totalassociated with the respective fibers increasing from a low for X1 andX1 to a high for X4 and X4, respectively, for example. By thisarrangement the sensitivity of the bridge circuit to changes inresistance of the photocells is made to decrease from the central fibersto the outside fibers.

The other two arms of the bridge circuit 64X contain resistors 65X and65X, respectively. Across the bridge between the filamentary photocellgroups 62X and 62X and between the resistors 65X and 65X there isconnected a generator 67X, which may be AC. or DC. generator, accordingto the particular needs of various situations. Connected in series withthe generator is a resistor 68X, the voltage drop across which isapplied as will be explained hereafter. The output of the bridge circuitis taken from the intermediate terminals thereof in the usual manner.

It will be understood that the Y coordinate bridge circuit 64Y isprovided with'the filamentary photocells of the Y fibers in a similararrangement to that of the X coordinate bridge circuit '64X, althoughthe Y bridge circuit has not been illustrated in detail.

Driving the scanning head along to follow the curve C requires that oneof the drive means, X motor 56 or Y motor 38, runs independently of thecurve as an independent variable. The other drive means can thenfunction as curve following means to move the scanning head parallel tothe other axes as a dependent variable when the curve moves off centerof the scanning head 11. Assuming, for example, that the scanning headis being driven parallel to the Y-axis by movement of the carriage 14along the bridge 15 in a motion independent of the curve by drive motor38, then drive motor 56 which positions the bridge along the X-axis willbe actuated as needed to keep the scanning head 11 centered on the curveC as the scanning heads Y-axis position successively changes. The actionis relatively simple. As long as the curve is centered so that itoverlaps an equal number of X fibers to the left and the right of center(the intersection X group of fiber ends with the Y group of fiber ends),the X coordinate bridge circuit 64X will be balanced and produce nooutput. However, as the Y-axis coordinate is changed by its independentdrive, this balance ceases; for example, when the scanning head is movedupward in the Y direction, fiber end X1 will be exposed to light whilefiber end X1 remains darkened and fiber end X2 is also darkened. Theflow of light to the respective illuminated filamentary photocellsreduces their resistance whereas the darkened photocells increase inresistance. Therefore, the accumulated resistance of photocell group 62Xin the selected example becomes less than the accumulated resistance ofphotocell group 62X. This causes unbalance of the bridge circuit,thereby producing a flow of current out of the bridge. This flow ofcurrent is of such a polarity acting through amplifier 7 1X and drivingmotor 56 in such a direction as to move the scanning head laterally tothe right until fibers X1 and X1 again cover the curve. If fibers X2, X3and X4 as well as fibers X2, X3 and X4 all or corresponding fibers onboth sides of center assume the same lighting conditions, the bridgecircuit returns to a balanced condition. Such step wise adjustment maycontinue in this manner with the dependent variable drive connecting theposition of one coordinate by sensing while the independent variablesuccessively and independently is changed by the other drive means. Inthis manner, many curves may readily be followed.

It will be observed that if the independent motion had been downwardinstead of upward, the fiber X1 would have become illuminated and fiberX2 would have become darkened causing an imbalance of the bridge in theopposite direction, a current flow in the opposite direction and anoperation of motor 56 in the opposite direction. Thus it will appearthat for certain types of curve following operations the type ofoperation of the scanning head and system of FIG. 4 thus far describedis all that is required. However, many curves are not satisfactorilyfollowed in this manner because at some point the curve comes close toparalleling the fiber array (in the case described the X fiber array)which is being used to center the scanning head along the curve. In suchinstances the orthogonal fiber array shown in FIG. 9 may be employedtogether with the overall system shown schematically therein in order topermit a switching from the Y motor 38 as the independent drive with theX motor 56 as the dependent drive scanning head curve-centering means tothe reverse situation in which the independent drive motion is producedby motor 56 in the X-axis direction and the Y motor 38 becomes thedependent drive means for centering the scanning head along the curve.More specifically, the fibers Y1, Y2, Y3 and Y4 and Y1, Y2, Y3 and Y4would act on their bridge circuit 64Y in this event exactly as the Xfibers acted on their bridge circuit 64X. As previously stated, the Yfibers terminate in photocells in bridge circuit 64Y, which would have aconfiguration the same as X coordinate bridge circuit 64X. Also, theoutput of the bridge circuit 64Y is connectable to a suitable amplifier71Y for operating Y motor 38. The operation of the Y bridge circuit andrelated connections is exactly the same as that described in regard tothe X bridge circuit and related connections.

The selection of whether the X or Y motor will be the independent drivemotor and which motor will be the dependent scanning head centeringdrive motor may be determined by an X-Y selection relay generallydesignated 75, which consists of a pivoted member 76 pivotable aboutpivot point 77 and having, for example, coils 78X and 78Y on oppositesides of the pivot connected across the sensing resistors 68X and 68Y,respectively, through appropriate amplifiers 79X and 79Y, respectively.The pivoted member 76 may itself be composed of iron or may be providedwith iron cores which are rotated about the pivot one way or the otherin accordance with the relative strengths of the magnetic pull of therespective coils 78X and 78Y. These coils may have their own iron coreswhich attract opposite ends of pivoted member 76 which may be ofmagnetic material or may act upon iron cores attached to the pivotedmember. The relative magnetic pulls of coils 78X and 78Y may have theoverall effect of a snap action since one coil will tend to hold thepivoted member in one position until that force is overcome by the forceexerted by the other coil. Alternatively, mechanical snap action may beprovided by one of the known mechanical overcenter expedients. Thepivoted member closes contacts 80X or 80Y by providing a conductiveconnection between each terminal pair. Closing contacts 80X or 80Y,respectively, energizes a conventional relay 82X or 82Y, respectively,by virtue of batteries 83X or 83Y in their respective circuits. Relay82X and relay 82Y actuate double ganged switches 85X or 85Y,respectively, such that when the relay 82X is energized, relay 82Y willbe deenergized and vice versa.

The operation of X-Y selection relay 75 is such that its pivot positionis determined by the difference in current flow through the sensingresistors 68X and 68Y in CTI series with the bridge circuit powersupplies, the coil 78X or 7 SY experiencing the greater current flowwill cause the relay to be actuated. The switch X or 80Y closesenergizing its relay 82X or 82Y, thereby closing switch X or 85Y to anindependent source of power 88X or 88Y to drive motor 56 or 38,respectively. For example, if coil 78Y receives greater current flowfrom brige circuit 64Y then coil 78X receives from bridge circuit 64X,pivot member 76 will be drawn toward coil 78Y closing contacts 80X.Closing contacts 80X will thereby energize relay 82X to actuate switch85X to connect X motor 56 to an independent power source whose output,however, varies in accordance with the integrating potentiometer 91X.The relay which is not energized by the X-Y selection relay 76 leavesthe bridge circuit 64Y connected to Y motor 38 through switches 85Y inits normal position. In this manner the connection of the dependentvariable scanning-head curve-centering actuating means to its dependentvariable motor is accomplished and acts as previously described. Itshould be explained in passing that the amplifiers 71X and 71Y are motorpower amplifiers of a conventional type and the motors 38 and 56,respectively, may be either DC. motors or two-phase AC. motors dependingon the type of overall system used. With the DC. motor, the armaturereceives the signal, Whereas with the two-phase AC. motor, the variablephase receives the signal.

Referring now to FIG. 5, a diagram is shown which illustrates thecoordinate fibers of scanning head 11 in a position wherein more X thanY coordinate fibers are darkened as the result of light reflection fromthe sheet being cut off by the line C. Line C, of course, absorbs lightrather than reflecting it as does the surrounding lighter area. Let usassume that the X-axis in this illustration has been the axis alongwhich the independent drive has been proceeding. Now, however, more ofthe X than Y fibers are deprived of light. As a consequence the totalresistance of the filamentary photocells in the X bridge circuit 64X ishigher than the total resistance of the filamentary photocells in the Ybridge 64Y since more Y photocells are energized by illumination andhence have their resistance reduced. Therefore, the current flow fromgenerator 67X through resistor 68X, designated as I will be less thanthe current I from generator 67Y flowing through resistor 68Y.Consequently, since the current through the solenoid 78X is less thanthe current through solenoid 78Y, the pivoted member 76 of X-Y selectionrelay will pivot point 77 toward relay core 78Y and will complete thecircuit through contacts 80X, thus energizing solenoid 82X and pullingthe switch 85X into its upper closed position so that the X motor isthen connected across the output of independent voltage source 88X,which will be explained in detail hereafter. Although the voltage source88X is variable, it is independent of position of the scanning head andwill keep the X motor driving the scanning head in the X direction,which will be either positive or negative depending on which wasselected. This condition will continue until the condition of switches81X and 81Y is reversed in the reverse of the manner described above asthe result of more Y fiber ends being covered by the curve than X fiberends (the reverse of the situation pictured in FIG. 5 i

The independent power supplies 88X and 88Y will now be explained. 'Itwill be noted that each independent power supply has a power source 90Xor 90Y, respectively, which may be either an AC. or a DC. source just aspower source 67X and 67Y may be, and the two are normally of the sametype. In either event, the generator 90X is connected in parallel with apair of parallel connected potentiometer elements 91X and 92X andgenerator 90Y is similarly connected with potentiometer 91Y and 92Y.Themovahle taps 93X and 93Y of the potentiometers 91X and 91Y,respectively, are manually set to a selected position which may be themidpoint. The movable taps 94X and 94Y of potentiometers 92X and MY,respectively, are positioned by shafts 95X and 95Y, which are driventhrough clutches 96X and 96Y, respectively, by the respective shafts ofmotors 56 and 38. The nature of the clutch is such that when the stop ateither end of the potentiometer resistance is reached, the clutch willslip thereafter as long as the drive continues in the same direction.This arrangement serves to produce a sort of integration of the trend bythe dependent variable drive motor as it follows the curve in all itsturns. If tap 94X is in the corresponding position of tap 93X, no outputwill appear across these two taps. Otherwise, however, when tap 94X ismoved to one side of the potentiometer 92X, the power source is incondition to produce a productive output, whereas as it moves to theother side of potentiometer, the power source is in condition to producea negative output in the event of switching of the independent anddependent drives as described above. A positive output will cause themotor 56 to drive in one direction and a negative output will cause themotor 56 to drive in the opposite direction. The Y coordinateindependent voltage source 88Y is similar in operation to source 88X.From the foregoing, it should be apparent that integration of the trendaccomplished by the dependent drive effectively causes slight changes inthe potentiometer position with each adjustment of the scanning headactuated thereby. For example, positive Y corrections will indicate thatthe curve is trending in the plus, Y direction and should be followed onthat course when switching to independent motion along the Y-axis.Conversely, if the Y corrections of the dependent drive are in thenegative direction, a negative drive will be imposed on motor 38 when itbecomes energized as the independent drive. In almost all instances,when switching occurs (for example, from the X-axis to Y-axis as theindependent drive), the position of the potentiometer tap (e.g. tap 94Y)will be such that the independent drive will operate to cause the drivemotor to rotate in the proper direction to permit the scanning head tocontinue to follow the curve in the proper direction. Only on very rareoccasions may some manual correction be needed.

It can be imagined how various modified configurations of fiberlocations in the scanning head might be used. For example, the Y shapedarrangement of FIG. 6 or of FIG. 8 might be used in connection with atriangular graphing arrangement with three axes. Of course, the logicand drive arrangements would have to be different from the XY coordinatesystem described above, but the system might be of much the same type.The fanned out array of fibers, as in FIG. 8, can be employed with thiscoordinate system and might be selected for use in any system requiringgreater sensitivity as deviation from the center of the scanning headoccurs.

The use of the FIG. 9 scanning head arrangement,

which is similar to the FIG. 10 arrangement previously mentioned, isbest limited to a situation in which the curve does not tend to haveportions that approach parallelism with the row of optical fiber ends.

The sensing head arrangement of FIG. 7 shows the preferred coordinatearrangement described in connection with FIGS. 4 and 5.

In all cases, the fiber ends in the scanning head are kept small withrespect to the line to be followed and preferably sufficiently closespaced that a transverse section of the line being followed will overlaptwo or more of the fibers at all times. It will be obvious that thecleaner cut the edges of the curve, the better the job of followingwhich can be done, but some degree of versatility is provided by thepresent system.

As previously stated, FIG. 10 is illustrative of the bottom of the codesensing head and is equally representative of sensing head rotated 90about its principal axes, both of which operate in the same manner inconjunction with their associated coded scales but have their fiber endgroupings normal to one another. FIG. 12 is a schematic diagram of theoptical fibers and associated apparatus embodied in the sensing heads 35and 45, respectively. The fibers are held in a fixed spaced relationshipin the scale sensing head 102 which may be a suitable transparentresinous material, being cast therein. The fibers are advantageously ina linear array normal to the code as shown in FIG. 10. Each of theoptical fibers 100 has an associated photocell 104 for converting alight effect into an electrical eiiect, as described in my co-pendingapplication entitled Filamentary Photocell Device. Beneath the ends ofthe optical fibers 100 is the previously mentioned coded scale 23 on thebase 10. The coded scale may be of the binary coded decimal typepartially shown in FIG. 11. Each of the units, tens, hundreds andthousands digits on scale 23 in FIG. 11 is represented by four columnswhich are needed to represent in binary form numbers between 0 and 9 ineach successive position of units, tens, hundreds and thousands areas.The code serves as a scale measuring the distance from a selected originalong the selected axis, here the Y axis. The binary coding is effectedin a particular row of increments of the columns sensed by the head byproviding light and dark areas, providing light reflecting and lightabsorbing areas, respectively. As the sensing head moves along thescale, the pattern changes in accordance with position in accordancewith the calibration of the system. The four columns of Arabic numbers,generally designated 110, to the left of the coded scale represent thecyclic decimal number designations corresponding to the binary codedareas along the same row. These decimal numbers do not actually appearon the scale of course but have been reset here for convenience inidentifying the code pattern. Various unit-distance codes, such as Graycode, may be used. It will be appreciated by those skilled in the artthat fiber optics easily makes possible rows less than a hundredth andeven less than a thousandth of an inch wide in the direction of movementof the sensing head.

Referring again to FIG. 12, the output of each of the photocells 104associated with fibers 100 is coupled by electrical connection, such asconnection 112, to a readback converter 114. The readback converter 114correlates and stores the coordinate information sensed by the opticalfibers 100 in a conventional manner. Thus, as the sensing heads 45 and35 move along the respective X and Y axes over the scales 46 and 23, isillustrated in FIG. 1, the coordinates locating of the scanning head 11with respect to the X and Y axes are identified and recorded together inthe readback converter 114. By taking successive readings as the curveis followed, the shape of the curve can be recorded in as much detail asis required, more detail being provided by recording more frequentposition readings. Of course, instead of storing the output of thesensing heads, the information might be used immediately and not stored.Reading may be taken at selected time intervals using a suitable timerto permit reading or recording automatically the coordinate information.Alternatively, after a predetermined number of code rows along theindependent axis, readings may be programmed.

A sensing head of the present invention, like that shown in FIG. 12, maybe used to create as well as read a coded scale in various binary codes.As shown in FIG. 12, each of the optical fibers 100 is provided with asmall discretely energized light source each fiber being arranged totransmit light only from its associated light source. In recording, thefibers retain the arrangement in groups of four for each of the units,tens, hundreds and thousands digits representations used in reading. Thelight sources are electrically connected to power through switch meanscontrolled by an input encoder 122 which sequentially energizes theproper combinations of light sources in accordance with the desiredcoding pattern, in accordance With the position of the sensing head atthe time. Beneath the scanning head 102, there is located aphotosensitive sheet or light affectable surface, preferable film with aphotographic emulsion thereon having selected areas in successive rowsexposed as the sensing head moves along the sheet to make the scale. Thedrive for the sensing head is synchronized with or drives the inputencoder which may be a precision shaft encoder having gear like codewheels, one for each fiber, which actuate switches open and closed inthe predetermined pattern necessary to produce the code. Alternatively,the encoder may have a commutator with conductive areas beneath brusheswhen the lights are to be on and insulating areas beneath the brusheswhen the lights are to be otf. In that case at least one brush and onetrack are required for each light. In cases requiring creation of ascale at a higher speed than permitted by the time constant ofincandescent filaments, small gas discharge sources of light may be usedfor the light sources 120. After the scale has been exposed inaccordance with the process adopted, it must, of course, be developed bya suitable process in accordance with known techniques. This may be donewith the scale in place using some techniques or alternatively the scalemay be taken up and replaced in proper position after being developed.

In accordance with the present invention, other applications for codesof the type described above are visualized and other apparatus forreading or creating coded scales are possible. For example, FIG. 13illustrates an apparatus which may be used to create or read codes ofthe general type shown in FIG. 11. A linear array of optical fibers 130is shown, the optical fibers being divided into four groups of fourfibers representing units, tens, hundreds and thousands digits and aseventeenth fiber for tracking purposes. Each of the optical fibers 130has associated with it a photocell, the output of which is coupled byelectrical connectors, such as illustrated with connectors 132, to areadback converter 136. The readback converter 136 in FIG. 13 operatesin the same manner as described in regard to the readback converter ofFIGS. 1 and 12. Each optical fiber 130 has associated with it a separatelight source 138 which is coupled to an input encoder 140, whichpreferably operates in the same manner as the input encoder of FIG. 12.Beneath the optical fibers 130 is the scale or sheet to be coded 142.The sheet is coded by selectively providing transparent or opaque areasas the alternatives of binary coding. If the sheet is to be coded, itmay not yet be transparent in any area but provide a light affectedsurface which can be photographically or otherwise processed to make thecode of transparent and opaque areas. The sheet 142 is secured on atransparent drum 144 so that its columns extend around the drum and itsrows extend along elements of the drum. The rotation of the drum isproduced by motor 146 such that the columns on the sheet move past therow of optical fibers 130 in the fixed sensing head. After a coded scalehas been created, the digital representation in the binary system may bereadback constant by illumination of the light sources 148 behind eachcolumn and associated in turn with each of the optical fibers 130.Opaque areas will then block light whereas transparent areas will permitlight to pass to the optical fibers for accurate reading of the codedscale. This technique permits reading and recording codes of microscopicsize much reduced over the size shown in FIG. 13. Alignment of the scalein relation to the fibers must be maintained and is particularlydifiicult with ultra small scales. This is accomplished, however, byoptical fiber 150 and associated photoelectric cell 152 to sense andtrack an opaque guide line 154 on the transparent sheet 142. The guideline 154 is made simultaneously with the coded scale by a light source155 whose light is transmitted by fiber 150 to continuously expose acolumn on the light sensitive sheet. After development, when a readbackoperation is being performed, an associated light source in drum 144 ispro- '12 vided for illuminating the area of the scale beneath fiber 150.The fiber tracks the margin of line 154 helping a balance between theadjacent light and dark areas. Whenever fiber 150 moves off the marginof guide line 154, it will be returned by the associated apparatuselectrically coupled to the photocell 152.

The photocell 152 is electrically coupled to a bridge or other device156 which controls the operation of a reversible motor 158 in suchmanner to drive in one direction to restore the balance upon decrease inthe amount of light and in the other direction to restore the balanceupon increase in the amount of light. Motor 158 operates to turn a worm160 meshing with a sleeve 162 of a movable bearing which controls theaxial position of the drum 144 on its drive shaft. If desired, aplurality of optical fibers having photoelectric cells and an associatedbridge circuit similar to that described in FIG. 4 may be used forfollowing the guide line 154 and positioning the drum and scale.

FIG. 14 illustrates an alternative embodiment of the apparatus of FIG.13 used to create or read coded scales. In FIG. 14, numberscorresponding to those used in FIG. 13 with the addition of primesthereto identify parts corresponding in function. FIG. 14 differs fromFIG. 13 in that a single light source is used to illuminate the codedscale 171, which in this case is not a transparent sheet, during areadback operation, and the coded scale 171 is secured on a continuousbelt arrangement by four rollers 172, 174, 176 and 178 spaced to movethe sheet arranged with its columns parallel to the edges of the belt.In FIG. 14 roller 172 is driven by motor 146 to move the sheet 171beneath the sensing head.

Other modifications of the optical fiber transducer and its systemdescribed herein will occur to those skilled in the art. All suchmodifications are intended to be Within the scope and spirit of thepresent invention as defined by the appended claims.

I claim:

1. Optical fiber transducer curve following apparatus comprising incombination, a curve support base on which a curve illustration may belocated,

bridge means movable across the curve support base in a predeterminedmanner,

bridge drive means for driving said bridge means across said curvesupport base,

a scanning head movably supported on said bridge means to move in apredetermined path along said bridge means transverse to the directionof movement of said bridge means,

said scanning head comprising a plurality of optical fibers having theirends in a closely grouped array and positioned to pick up lightreflected from said curve illustration,

a plurality of photocells each photocell associated with a different oneof said fibers,

scanning head drive means for moving said scanning head along saidbridge means,

first circuit means for connecting at least some of said photocells toone of said drive means to cause said one drive means to center saidscanning head on said curve being followed by said scanning head,

second circuit means for connecting the other of said drive means to asource of power to operate as an independent drive means,

third circuit means for connecting the other than the at least some ofsaid photocells to the said other of said drive means to cause saidother drive means to center said scanning head on said curve beingfollowed by said scanning head, and

switch means for changing from the arrangement in which said firstcircuit means is connected to one drive means and said second circuitmeans is connccted to the other drive means to the arrangement in whichsaid second circuit means is connected to 13 the one drive means andsaid third circuit means is connected to the other drive means.

2. The apparatus of claim 1 in which the respective groups of fibersassociated with the respective groups of photocells associated with thefirst and third circuit means are arranged in patterns mutuallytransverse to one another across said scanning head.

3. The apparatus of claim 2 in which said first and third circuit meansalternatively connecting their respective groups of said photocells tosaid one drive means and said other drive means, respectively, comprisebridge circuits, each having a pair of input terminals and a pair ofoutput terminals, each bridge circuit having connected in two armsthereof photocells from optical fibers of one of the mutually transversegroups, those fibers at one side of the intersection of the two groupsbeing connected in one arm of the bridge and those fibers at the otherside of the intersection being connected to the other arm of the bridge.

4. The apparatus of claim 3 in which said photocells are connected inparallel in each of said arms, said apparatus further comprising meansfor varying the sensitivity of said bridge such that the photocellsassociated with fibers nearer the intersection have greatest effect onrestoring forces than do more remotely located fibers.

5. The apparatus of claim 4 in which said switch means comprises:

a selection relay having two contact positions;

sensing means located one in each of said bridge circuits for providingan output indicative of current flow in said bridge circuit;

actuator means associated with each of said sensing means responsive tothe output of each thereof for actuating said selection relay betweenits two contact positions for connecting alternatively one of saidbridge circuits to one of said drive means, the other drive means beingconnected to said second circuit means.

6. Optical fiber transducer scale sensing means comprising incombination:

support base means;

bridge means providing a movable member movable in a predeterminedmanner relative to the base across said base;

bridge drive means for driving said bridge means across said base;

a carriage providing a movable member movable in a predetermined mannerrelative to said bridge means on said bridge means transverse to thedirection of movement of said bridge means;

carriage drive means for moving said carriage across said bridge means;

a scale sensing head located on one of said movable members;

a scale having columns and cooperating with said scale sensing headlocated on the means relative to which said one movable member ismovable in a predetermined manner; and

said scale sensing head comprising an array of optical fibers whose endsare fixed relative to one another so that each fiber scans one of saidcolumns of said scale.

7. The optical fiber transducer scale sensing means of claim 6 furthercomprising a plurality of photocells each photocell associated with adifferent one of said fibers, and storage means electrically coupled toeach of said photocells for identifying and storing information scannedby said fibers.

'8. The optical fiber transducer scale sensing means of claim 6 in whicha scale sensing head is located on each of the movable members and ascale cooperating with the scale sensing head is provided for each ofsaid sensing heads.

9. Optical fiber transducer means comprising in combination:

a support base means;

bridge means providing a movable member movable in a predeterminedmanner relative to the base across said base;

bridge drive means for moving said bridge means across said base;

a carriage providing a movable member movable in a predetermined mannerrelative to said bridge means on said bridge means transverse to thedirection of movement of said bridge means;

carriage drive means for moving said carriage along said bridge means;

a sensing head located on one of said movable members;

a light senstitive sheet cooperating with said sensing head located onthe means relative to which said one movable member is movable in apredetermined manner and having a light affectable surface;

said sensing head comprising an array of optical fibers whose ends arefixed relative to one another so as to scan columns on said sheet;

a plurality of light sources, each light source associated with adifferent one of said fibers;

encoder means to selectively light and extinguish said light sources inaccordance with a predetermined sequence;

whereby successive incremental positions of said sensing head as it ismoved along said sheet by said movable member are exposed in patterns oflight afiecting said light afiectable surface, which patterns whendeveloped provide a coded scale indicative of said incrementalpositions.

10. The optical fiber transducer means of claim 9 further comprising aplurality of photocells each photocell associated with a different oneof said fibers, and storage means electrically connected to each of saidphotocells for identifying and storing information sensed by saidfibers, as from a coded scale, produced by said sensing head.

11. A method of making a coded scale having columns representing codednumbers comprising:

providing a light sensitive sheet having a light afiectable surface;

driving a sensing head having an array of optical fibers along saidsheet past a plurality of selected stations;

lighting and extinguishing individual light sources associated with eachof the respective fibers to transmit light in a unique pattern throughsaid optical fibers at each selected station; and

developing said sheet to provide a coded record representative of thesuccessive selected stations of said sensing head along said sheet.

12. A method of following a curve comprising:

positioning a scanning head to sense a curve in one position,

driving said scanning head with an independent drive past the curve,

producing an error signal each time the scanning head departs from thecurve,

moving said scanning head in response to error signals by a dependentdrive as said independent drive progresses to cause the scanning head tofollow the curve, and

upon the sensing of a predetermined change in orientation of the curveinterchanging the independent and dependent drives.

13. A method of following a curve positioned with respect to a pair ofmutually perpendicular axes comprising:

driving a scanning head with an independent drive along one of saidaxes,

moving said scanning head in accordance with variations in position ofsaid curve by a dependent drive 15 relative to the other of said axes asthe independent drive progresses, and

changing the independent drive and dependent drive between the difierentaxes when said curve approaehes paralleling the axis associated withsaid dependent drive.

14. Optical fiber transducer means comprising:

a sensing head including an array of optical fibers whose ends are fixedrelative to one another;

1 a light sensitive sheet having a light aifectable surface and locatedalong the path of movement of said ends of said optical fibers for beingexposed by light therefrom;

drive means for producing relative movement between said sheet and saidsensing head;

a plurality of light sources each light source associated with adifferent one of said fibers; and

encoder means for selectively energizing and extinguishing said lightsources in accordance with a predetermined sequence, whereby said fiberstransmit said light toward said sheet for exposing or not exposingsuccessive increments in columns on said sheet defined by the locationsof the respective optical fibers.

15. The optical fiber transducer means of claim 14 further comprising aplurality of photocells, each photocell associated with a different oneof said fibers, and storage means electrically connected to each of saidphotocells for identifying and storing information transmitted throughsaid photocells from said light sources or from a scale.

16. The optical fiber transducer means of claim 15 in which light sourcemeans is provided for illuminating a 16 coded scale moving relative tosaid sensing head beneath said sensing head in response to said drivemeans, whereby said fibers will pick up light from said scale forreading incremental positions indicated on said scale, said light beingpicked up by said fibers and transmittedthrough said photocells to saidstorage means.

References Cited UNITED STATES PATENTS 2,423,440 7/1947 De Neergaard250202 X 2,838,683 6/1958 Munro 250202 X 2,951,736 9/ 1960 Black.

3,029,717 4/1962 Hildebrandt 350-96 X 3,104,324 9/1963 Rabinow 250--2273,106,706 10/ 1963 Kolanowski et al.

3,113,313 12/1963 Roberts 346-31 X 3,198,949 8/1965 Holdo 2502023,310,681 3/1967 Hargens 250227 3,335,287 8/1967 Hargens 2502273,354,319 11/1967 Loewen et al 250227 FOREIGN PATENTS 898,516 6/1962Great Britain.

OTHER REFERENCES 'Hamrick et al., IBM Technical Disclosure, vol. 4, No.7, December 1961, p. 85.

Sharp, IBM Technical Disclosure, vol. 5, N0. 3, August 1962, p. 14.

RALPH G. NILSON, Primary Examiner.

M. A. LEAVITT, Assistant Examiner.

U.S. DEPARTMENT OF COMMERCE PATENT OFFICE Washington, 0.0. 20231 UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,403,263September 24, 1968 Charles W. Hargens III It is certified that errorappears in the above identified patent and that said Letters Patent arehereby corrected as shown below:

Column 1, line 66, "elertrical" should read electrical Column 2, line 3,"conduit" should read conduct Column 4 line 23, beginning with "11 tosense" cancel all to and includin "monitoredl' in line 26, same column4, and insert head in the X-axis direction. The combination of movementsalong the X- and Y-axes enables the scanning head 11 to sense anycoordinate posi tion over the total area being monitored. line 53,cancel "across, second occurrence. Column 8, line 8, "then" should rethan Column 9, line 14, "productive" should read posi tive Column 10,line 47, "is should read as Signed and sealed this 24th day of February1970.

(SEAL) Attest: Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents

